Expansion and tensioning device for aluminum alloy pistons



March 5, 1940. I J MOELLER 2,192,323

EXPANSION AND TENSIONING DEVICE FOR ALUMINUM ALLOY PISTONS Original Filed Sept. 30, 1933 $761 5 Hag,

J mum UNITED STATES PATENT OFFICE EXPANSION AND TENSIONING DEVICE FOR ALUMINUM ALLOY PISTONS George J. Moeller, Maplewood, Mo., assignor to Ramsey Accessories Manufacturing Corporation, St. Louis, Mo., a corporation of Missouri Substitute for abandoned application Serial No.

691,612, September 30, 1933.

This application January 26, 1934, Serial No. 708,361

1 Claim.

My invention has relation to improvements in expansion and tensioning devices for aluminum alloy pistons and it consists in the novel features of construction more fully set forth in the specification and pointed out in the claims. The present application is a substitute for that heretofore filed September 30, 1933, on the same subject-matter by Charles A. Marien and myself under Serial No. 691,612.

It is a matter of common knowledge in the automotive industry that alloy pistons must be longitudinally slotted in order to allow for the unequal degree of expansion between the pistons and the cast iron cylinders. This slot introduces an element of weakness in the piston structure ultimately causing the piston to collapse in the lower part of the skirt and introducing a piston slap in operation. It has heretofore been proposed to correct this condition by placing steel expanding rings in the lower part of the skirt to restore the piston to its proper shape and reenforce the skirt so that it will again ride squarely on the cylinder wall and possess the proper degree of resiliency so that it will yield to excessive pressures placed upon it due to inequalities in the expansion of said cylinder wall. In the patent of Harold F. Phillips, Reissue No. 18,653, dated November 15, 1932, the principle of expanding a piston skirt in a direction at right angles to the pin bosses is disclosed, and in the patent of Charles A. Marien, No. 1,887,769, dated November 15, 1932, a particular type of expanding ring is shown wherein the expanding ring is so shaped that pressure at right angles to the pin bosses is assured.

However, in both of these patents the construction of the piston is relied on to secure the expander in place. Some pistons are so constructed as not to present appropriate recesses, or other formations for holding the expander ring in place, in which event the expander itself must be provided with the elements for securing it in place.

It is the object of the present invention to provide a skirt expander that may be anchored either on the piston pin or the piston pin bosses, said expander having skirt expanding parts projecting downwardly from the point of anchorage to be effective on the lower part of the skirt by exerting tension thereon at right angles to the axis of the pin bosses. The present invention contemplates two forms of such elements, one of which may be made of spring wire bent into the proper shape to perform its function, and the other comprising a stamping of spring steel subserving the same function in the same way as the wire expander.

A further object of the invention is to provide an expander that may be effectively secured in the piston and which is durable and long-lived, although it may be cheaply manufactured. Other advantages inherent in the invention will be better apparent from a detailed description of the same in connection with the accompanying drawing, in which:

Figure 1 is a side elevation of a longitudinally slotted piston with part of the wall broken away to show my improved skirt expander securely fixed within the skirt; Fig. 2 is a bottom plan of the piston showing the skirt expander lodged therein; Fig. 3 is a vertical longitudinal section taken on the line 3-3 of Fig. 1; Fig. 4 is a perspective view of the expander (shown in Figs. 1 to 3, inclusive) removed from the piston skirt and, of course, not under tension; Figs. 5, 6 and 7 are views corresponding to Figs. 1, 2 and 3, respectively, showing a modified form of expander produced from sheet metal instead of wire; and Fig. 8 is a development of the modified form of expander showing the shape of the stamping before the same is formed so as to perform its spring function.

Referring to the drawing, P represents a piston provided with the usual pin bosses I, I in which the piston pin 2 is lodged and having a longitudinally disposed slot 3 in the piston skirt 4, according to the practice now common in the art. E represents my improved expander bent from a suitable length of spring wire so as to have oppositely disposed U-shaped spring arms or wings 6, 6 connected by axially alined coils 1, 1 centrally disposed with respect to the arms 6, 6, said coils serving as the hinge point for the arms 6, 6. The wire 5 is preferably bent so that the ends will come together at the end of one of the arms 6, as shown at 8, and they are then effectively secured together by welding, or brazing, or soldering. The coils or lobes I, I are of sufficient diameter so that they will receive the piston pin bosses l, I, as shown in Figs. 1 to 3, inclusive. The U-shaped spring arms 6, 6 when not under tension make a considerably greater angle with each other than when they are under tension by confinement within the skirt 4 of the piston, although the tension may be regulated by varying this angle so that the correct amount of tension may be obtained to give most satisfactory results on pistons of different design. The cross elements 6', 6' at the ends of the spring arms 6, 6 are preferably arcuate so that they will llUUl'l fit snugly within the piston skirt and contact therewith throughout their entire length (as shown in Fig. 2).

In the modification shown in Figs. 5 to 8, inclusive, the expander E is formed from a stamping l0, said stamping having oppositely disposed wings H, II embossed, as shown at l2, for increasing their strength, and oppositely disposed lobes l3, l3 at right angles to the wings II, II, said lobes each having an opening M to receive the piston pin 2 when the expander is inserted within the piston. The stamping I is given its proper shape by bending the lobes l3, l3 along the dotted lines 2:, :1: shown on the connecting necks I5, l5 between the wings H, II and lobes l3, l3. The lobes are bent at right angles to. the wing portions H, II of the stamping, after which the wing portions themselves are bent to substantially the shape shown by the dotted positions of the wings H, II in Fig. '7. The ends 9f the wings are formed with arcuate extremities I6, l6 for making contact with the bottom of the piston skirt, as shown in Figs. 5 to 7, inclusive. After the expander E has been bent to its proper shape it is, of course, properly tempered so that the wings II, I I, which perform the functions of spring arms when the expander is in the skirt, will have the proper tension to maintain the piston skirt properly expanded and offer the right amount of resistance to. the thrusts that are encountered as the piston operates in the engine cylinder.

While the invention is primarily adapted for use with aluminum alloy pistons, most of which have a longitudinally slotted skirt, as above pointed out, it is also useful in cast iron pistons, especially if they have comparatively thin walls, and pistons of other types. I do not, therefore, wish to be restricted to a tensioning device for use either in slotted skirt pistons or aluminum alloy pistons whether the skirt is slotted or not.

I Having described my invention, I claim:

In combination with a piston assembly, an ex- -pander in the piston skirt comprising a wire bent to form oppositely disposed U-shaped spring arms adapted to bear against thepiston skirt, corresponding sides of the U-shaped spring arms being connected by loops for securing the expander in the piston assembly.

GEORGE J. MOELLER. 

